An encrypted e-mail service believed to have been used by former U.S. intelligence contractor Edward Snowden has shut down.

On August 8, Ladar Levison, owner of Texas-based company Lavabit, said legal reasons prevented him from explaining his decision but said he would rather end the service than "become complicit in crimes against the American people."

Another encrypted e-mail provider, Silent Circle, also shut down its "Silent Mail" service on August 8.

In a statement to the website Tech Crunch, the company's CEO said, "We wanted to be proactive because we knew [the U.S. government] would come after us."

Snowden has admitted leaking information about U.S. Internet- and telephone-surveillance programs.

On August 1, Russia granted him temporary asylum, raising tensions between Washington and Moscow.